1. Field of the Invention
The present invention relates to a method of lowering the electrical resistance of soils and to grounding electrodes comprising a volume of soil of lowered electrical resistance.
2. Description of the Prior Art
For safety and operational reasons it is common practice to ground electrical installations, such as power line towers and metal substation structures, by connecting the installation to the earth. One typical way of accomplishing this grounding is to bury metallic electrical conductors, such as a grid of copper rods, and connect the conductors to the installation. However, it is extremely expensive to use copper and other metallic conductors for grounding purposes. In addition, corrosion occurring at the surface of the metal reduces its effectiveness as a grounding connection. Also, the high scrap value of these materials makes them attractive to thieves.
It has been recognized that grounding is improved when an electrical installation is connected to soil having a lowered resistivity. To this end, copper sulfate and other salts have been spread on the surface so that they are carried underground when wetted, as by rain. These salts lower the resistivity of soil so that when a ground rod is driven into soil treated in this manner and connected to the electrical installation, improved grounding results. As an alternate method of applying salts to soil, salt filled tubes, such as shown in U.S. Pat. Nos. 3,582,531 and 3,930,111, have been buried. These tubes have openings which permit moisture to enter and carry the salts into the soil. Soil treating methods of these types are unsatisfactory because the salts leach from the treated soil. Consequently, only a temporary improvement in grounding results from such methods. More importantly, leaching of chemicals from treated soils can pollute ground water supplies and create other environmental problems.
These problems are only partially solved by treating soil with salts of low solubility such as described in U.S. Pat. No. 3,029,302.
In addition, injection of various other materials into the ground through hollow ground rods has also been explored. For example, U.S. Pat. No. 1,976,919 discloses the injection of a carbonaceous paste and U.S. Pat. No. 2,558,159 discloses the injection of substances which form an underground electrically conductive gel. U.S. Pat. No. 2,558,159 discloses still another substance which has been introduced into soil for grounding purposes.
However, none of these references discloses an improved soil treatment method in which the electrical conductivity of a volume of soil is enhanced by treatment with an electrolyte and the treated volume is at least partially enclosed within a water repellant electrically conductive layer bonded to additional soil surrounding the volume.